"Tropical beach" in continental Europe? [closed]

Plenty of places by the Mediterranean have sandy beaches. Northern Italy, near Venice, has some sandy beaches, and is even closer to you than Croatia. There will be villas for rent. However the area is fairly crowded, which may not satisfy your definition of 'tropical'.

The further south you go the more 'tropical' it gets. Greece is another good choice, and a boat ride will get you to an island where you can have a bit more privacy. Turkey is also an option if you don't mind going a bit further.

I believe the Russians find their tropical beaches on the Black Sea, but you may think of that as 'tropical' only if you're from Siberia.

May I suggest Tropical Islands Resort, in Germany? This is an indoor tropical environment, with beach, rainforest and accommodation, just 60km from Berlin.

I would assume "tropical beach" you mean tropical like beaches with warm sunny days?
Apparently the beaches near Catania, Sicily in Italy are very good and they are pretty warm during summer and some of them are long stretch and have private beaches too.

The island of Rügen has very nice sand beaches, for example between Glowe and Altenkirchen. It's also very very close to Poland. Houses and appartments can easily be rented and the available infrastructure is splendid.

The only downside is that temperatures don't compare to tropical regions. We had weeks with 30°C and very sunny stretches in the summer, but it being an island in the Baltic Sea, the weather can act up. So you might study its weather reports before going there and possibly getting a rainy week.